The image of Sully, the faithful service dog for George H. W. Bush sitting near the casket of the late former president, touched the hearts of many. Trained specifically to assist people who have disabilities, service dogs are up there with all those other canines, large and small, who serve humanity through bravery, support, or companionship.

Regimental mascot - Catherine, Duchess of Cambridge, presents a sprig of shamrock to the mascot of the 1st Battalion Irish Guards, an Irish Wolfhound called Domhnall, during a visit with her husband, Prince William, to a St Patrick's Day Parade at Mons Barracks in Aldershot, England.

Medical response dog - Macie, a small medical alert and response dog, pauses during her handler's shopping spree. These dogs are trained to help ease their handlers' symptoms, such as bringing medications or a telephone if the patient cannot reach one. (Photo: Wikimedia/CC BY-SA 4.0)

Diabetes alert dogs - Diabetes alert dogs like Shirley (left) that are partnered with diabetic people may be trained to detect when the handler's blood sugar becomes too high or low. The Labrador Retriever is pictured with sniffer dog Jake.

Psychiatric service dog - A psychiatric service dog pictured during training. These dogs are trained to assist their handler with a psychiatric disability or a mental disability. (Photo: Wikimedia/CC BY-SA 3.0)

Helping people who have disabilities - Another former soldier, who was shot and paralyzed during the Iraq war, sits with his service dog Yazmin while training at the Canine Companions for Independence training center in Santa Rosa, California, USA.

Helicopter hounds - A pair of US Coast Guard Maritime Safety & Security Team Belgian Malinois canines take part in helicopter proficiency training with the California Air National Guard in San Francisco Bay, USA.

Faithful friend - Sully, a yellow Labrador service dog for former President George H. W. Bush, sits near the casket of the late former President as he lies in state at the US Capitol, Washington, D.C., USA.

At our service: the dogs that help humanity

Celebrating the dogs who assist us all

The image of Sully, the faithful service dog for George H. W. Bush sitting near the casket of the late former president, touched the hearts of many. Trained specifically to assist people who have disabilities, service dogs are up there with all those other canines, large and small, who serve humanity through bravery, support, or companionship.